1. Field of the Invention
The present invention relates to a laminate-type heat exchanger preferably used as a heat exchanger such as an evaporator for use in an automobile air conditioning system.
2. Description of Related Art
Conventionally, a so-called laminate-type heat exchanger is well known as an evaporator for use in an automobile air conditioning system. As shown in FIGS. 23 to 25, the evaporator has a core 1 comprised of a plurality of tubular elements 2 laminated in the thickness direction thereof. Each tubular element is formed by coupling a pair of plate-shaped formed plates 5 and 5 in a face-to-face manner. In the intermediate portion of the tubular element 2, two refrigerant passages 3a and 3b extending in the direction of height of the core 1 are formed in parallel with each other, wherein one of the refrigerant passages 3b is located at the front side of the core 1 and the other 3a at the rear side of the core 1. At the upper and lower end portions of the tubular element 2, tank portions 4a and 4b communicating with the corresponding refrigerant passage 3a and 3b, respectively, are formed.
Furthermore, in the evaporator, the adjacent tubular elements 2 are communicated with each other via the predetermined tank portions 4a and 4b, whereby a first pass P1, a second pass P2, a third pass P3 and a fourth pass P4 are formed at the rear left portion, the rear right portion, the front right portion and the front left portion of the core 1, respectively. Between the second pass P2 and the third pass P3, the upper tank portions 4a and 4b of each tubular element 2 are communicated with each other to form a turn portion T.
The refrigerant flowed into the upper tank portions 4a of the first pass P1 flows downward through the first pass P1 to reach the lower tank portions 4a. Then, the refrigerant is introduced into the lower tank portions 4a of the second pass P2, and then flows upward through the second pass P2 to reach the upper tank portions 4a. Thereafter, the refrigerant is introduced into the upper tank portion 4b of the third pass P3 through the turn portion T between the second pass P2 and the third pass P3. Subsequently, the refrigerant flows downward through the third pass P3 to reach the lower tank portion 4b of the third pass P3, and then is introduced into the lower tank portion 4b of the fourth pass P4. Then, the refrigerant flows upward through the fourth pass P4, and flows out of the evaporator via the upper tank portions 4b.
In the meantime, while passing through each pass P1 to P4, the refrigerant exchanges heat with the air passing through the core 1 from the front side thereof toward the rear side to be evaporated by absorbing heat from the air.
In the aforementioned conventional evaporator, as shown in FIGS. 24 and 25, when the refrigerant is introduced into the lower tank portions 4a of the second pass P2 from the lower tank portions 4a of the first pass P1, the refrigerant flows through the lower tank portions 4a of the second pass P2 toward the other side (i.e., in the right direction R shown in FIG. 24). As a result, the refrigerant tends to pass through the right side region of the second pass P2 as shown by the oblique lines in FIG. 25 because of the fluidity and/or the inertia of the refrigerant. Then, the biased refrigerant is introduced into the turn portion T between the second pass P2 and the third pass P3 it: to reach the third pass P3. In the third pass P3, the biased state of the refrigerant flow further increases. This prevents an efficient heat exchanging at the entire area of the third pass P3, resulting in deterioration of the cooling performance.